This invention is directed to certain cobalt chelates and to an improved process for forming cobalt chelates and in particular, to alkyl cobalt (III) dioximates and a process that provides an improved yield and purity of such dioximates.
Cobalt chelates have been widely used in the polymerization of high and low molecular weight polymers, and in the formation of oligomers, macromoners, and latices. Also, cobalt (II) chelates have been used as chain transfer agents in free radical polymerizations to form polymers. Acrylic graft copolymers having an acrylic copolymer core and macromonomers grafted thereto have been prepared utilizing cobalt chelates. The synthesis of terminally unsaturated oligomers and functionalized diene oligomers using cobalt chelate catalysts also are known.
G. N. Schrauzer, Wingassen, J.Am.Chem.Soc 89(1967)1999, shows the formation of an alkyl chelate, i.e., an alkyl cobalt (III) dioximate, using dimethylglyoxime but the yield was low (45%) and purity less than 80%. The method when used with other glyoximes such as diphenylglyoxime, methylcarboxyethylglyoxime and methyldiphenylglyoxime did not form an alkyl cobalt (III) dioximate. There is a need for a process that will produce an alkyl cobalt (III) dioximate in a high yield and in a high purity. The process should allow for the formation of alkyl cobalt (III) dioximates by using glyoximes other than dimethylgloxime since such other glyoximes can impart important properties to the chelate, such as shelf stability and solubility in a variety of solvents. Such properties make the chelate more versatile and useful and cost effective in polymerization processes used for a variety of monomers.
This invention is directed to alkyl cobalt (III) dioximates and methods for making these dioximates. The alkyl cobalt (III) dioximate has the following structural formula: 
wherein R1, and R2, are individually selected from the following group: H, alkyl having at least 2 carbon atoms, substituted alkyl, aryl, substituted aryl, COOR5, CONR6R7, SR7, SO2R7, SO2NR5R6, SOR5, SO3R5, halogen, CCl3, CF3, COR5, CHO, CR6R7OR5, CH(OR5)(OR6), CR5(OR6)(OR7); where R5, R6, and R7 are independently selected from the following group: H, alkyl, substituted alkyl, aryl or substituted aryl and A is a substituted alkyl derived from an olefinic component and B is a component of a Lewis Base and where the substituents of the substituted alkyl are individually selected from the group of ester, ether, amide, halogen, ketone, hydroxy, aryl, SO2-alkyl, sulfamido, and amino groups and the substituents for the substituted aryl are individually selected from the group of ester, ether, amide, halogen, ketone, hydroxy, alkyl, SO2-alkyl, sulfamido, and amino groups.
The alkyl cobalt (III) dioximate of this invention is formed by a novel process in which a mixture of a cobalt (II) salt, a dioxime, an olefinic component and a Lewis base is treated with molecular hydrogen under pressure of 0.7 to 70 kg/cm2. The cobalt (II) salt, dioxime, olefinic component, and the Lewis base are reacted in a molar ratio of 1:2:1:1. Typically, the hydrogen is under a high pressure of 14 to 70 kg/cm2, preferably, 18 to 30 kg/cm2 unless a Lewis base of an imidazole, phosphine or phosphite is used. If such a Lewis base is used, the hydrogen pressure can be reduced to 0.7 to 14 kg/cm2 preferably, 1 to 2 kg/cm2. Typical treatment time with hydrogen under pressure is 0.5 to 5.0 hours, preferably 4 to 6 hours. Typical reaction temperatures are xe2x88x9220 to 50xc2x0 C. and preferably 17 to 30xc2x0 C.
Particular advantages of the novel process are that the yields are high, i.e., 70% and over and that the purity is high, 80% and over, of the alkyl cobalt (III) dioximate formed.
Typical cobalt (II) salts that can be used are acetates, nitrates, chlorides, bromides, iodides, fluorides, sulfates, fluoroborate, hexafluorophosphate or hexafluoroantimonate either as hydrated or anhydrous, or as an alkanoate. Mixtures of any of the aformentioned cobalt (II) salts also can be used. Lower (C2 to C3) alkanoates are soluble in methanol or propanol and the higher (C4 to C8) alkanoates are soluble in hydrocarbon solvents. Typical examples of the above cobalt salts are cobalt chloride, cobalt chloride hexahydrate, cobalt acetate, cobalt acetate tetrahydrate, cobalt nitrate, cobalt bromide, cobalt iodide, cobalt difluoride, cobalt ammonium sulfate and cobalt 2 -ethylhexanoate. Preferred are cobalt chloride hexahydrate and cobalt acetate tetrahydrate.
Typical dioximes that can be used have the structural formula R1xe2x80x94C(xe2x95x90NOH)xe2x80x94C(xe2x95x90NOH)xe2x80x94R2 where R1 and R2 are described above. Typical dioximes are as follows: diphenylglyoxime, carboxyethylmethylglyoxime, methyl phenylglyoxime, dimethylamidolcarbonylmethylglyoxime, 4-amidophenylamidylcarbonylmethylglyoxime, trifluoroacetyl-trifluoromethylglyoxime, camphordiquinonedioxime, 1,2-cyclohexanedioxime, furildioxime, thiophenylglyoxime, and di(butylthio)glyoxime. Preferred are diphenylglyoxime and carboxyethylmethylglyoxime.
A Lewis base is used in the process to form the cobalt (III) dioximate of this invention and forms the A component of the dioximate. It is believed that the Lewis base activates the cobalt in the reaction with hydrogen and forms a coordination bond with the cobalt. Typically useful Lewis bases are alcohols, such as methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, water (under some conditions); alkyl mercaptanes, such as ethyl mercaptane, thiophenole, dodecyl mercaptan; amines, such as pyridine, 4-methylpyridine, nicotineamide, 2-methyl pyridine, and 4-dimthylaminopyridine. Pyridine is preferred.
When imidazoles, phosphines or phosphites are used as the Lewis Base constituent, the pressure of molecular hydrogen can be lowered significantly as stated above. It is believed that when these three aforementioned compounds are used, they activate the cobalt in the reaction with hydrogen to a greater extent and hydrogen under a lower pressure, such as 0.7-14 kg/cm2, can be used. Typically useful imidazoles have the structural formula: 
wherein R8, R9, R10, and R11 are each selected from the following: H, alkyl, aryl, NR5, N6, SR7, SO2R7, SO2NR5R6, SOR5, COR5, CHO, CR6R7OR5, CH(OR5)(OR6), and CR5(OR6)(OR7); and where R5, R6, and R7 are each selected from the following group: H, alkyl and aryl. Examples of such imidazoles are as follows: unsubstituted imidazole, 2-methyl imidazole, 2-phenyl imidazole, 1,2 dimethyl imidazole, 1,2 diethyl imidazole, 1-methyl-2-ethyl imidazole, 1-butyl imidazole, and 2,5-dimethyl-4-hydroxymethyl imidazole. 1,2 Dimethyl imidazole and 1-butyl imidazole are preferred.
Phosphines that can be used have the formula P(R14)(R15)(R16), wherein R14, R15, R16 are each selected from the following group: H, alkyl and aryl. Typically useful phosphines used are triphenyl phosphine and triethyl phosphine.
Phosphites that can be used have the formula P(OR17)(OR18)(OR19), where R17, R18, and R19 are each selected from the following group: H, alkyl and aryl. Typically useful phosphites are triethylphosphite, triphenylphosphite, and tricresylphosphite.
The olefinic component included in the B component of the alkyl cobalt (III) dioximate forms a coordination bond with the cobalt constituent of the dioximate. Typically olefinic compounds that are used in the process of this invention are alkyl acrylates, i.e., alkyl esters of acrylic acid, such as methyl acrylate, ethyl acrylate, propyl acrylate, methoxy ethyl acrylate, phenoxy ethyl acrylate, isopropyl acrylate, butyl acrylate, pentyl acrylate, and ethylhexyl acrylate. Methyl acrylate is preferred.
Other olefinic components that can be suitably used such as styrene, methyl styrene, acrylonitrile, acrylamide, dimethylolacrylamide, vinyl pyrrolidone, vinyl chloride, vinyl acetate, maleic anhydride, N-methylmaleimide, and other vinylic monomers of the following structure: 
where X is an amide, imide, ester, aryl, halogen, pseudo halogen (thiocyanates), isocyanate, nitrile, ether, carbamyl, substituted amine and thio ether.
Suitable solvents that can be used in the process are alcohols, such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, and any mixtures thereof. Other common organic solvents that can be used are diethyl ether, ethylene glycol, polyethylene glycol monoalkyl and dialkyl ethers, propylene carbonate, N-methyl pyrrolidone, amides, dimethylsulfoxide, and Cellosolves(copyright) and Carbitols(copyright) both supplied by supplied by Union Carbide Corp. Danbury, Conn. Water and mixtures of water and the aforementioned solvents can be used.
The novel process of this invention provides for high purity alkyl cobalt (III) dioximate and in a high yield. Yields are 70% and over and preferably 75% and up to 100% and purity is over 80% and preferably over 85% up to 100%.
In one preferred alkyl cobalt (III) dioximate, R1 and R2 are phenyl, A is (methoxycarbonyl) ethyl and B is pyridine; in another preferred alkyl cobalt (III) dioximate, R1 and R2 are phenyl, A is (methoxycarbonyl) ethyl and B is dimethyl imidazole; in still another preferred alkyl cobalt (III) dioximate, R1 and R2 are phenyl, A is (methoxycarbonyl) ethyl and B is triphenylphosphine. The alkyl cobalt (III) dioximate is an excellent chain transfer agents used in free radical polymerization of polymers, macromonomers, oligomers, low molecular weight polymers (Mw 200 to 1,000), medium molecular weight polymers (Mw 1,000 to 50,000) and high molecular weight polymer (Mw 500,000 and over), latex polymers, graft copolymers, star polymers, hyperbranched polymers, core shell structured polymers and other polymer compositions.
The following examples illustrate the invention. All parts and percentages are on a weight basis unless otherwise indicated.